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1. Prepubertal gonadectomy reveals sex differences in approach-avoidance behavior in adult mice

   https://doi.org/10.1016/j.yhbeh.2019.104641  

   Delevich, Kristen; Hall, Chris D.; Piekarski, David; Zhang, Yuting; Wilbrecht, Linda (February 2020, Hormones and behavior)

   null (Ed.)

   Adolescence is a developmental period that is associated with physical, cognitive, and affective maturation and a time when sex biases in multiple psychiatric diseases emerge. While puberty onset marks the initiation of adolescence, it is unclear whether the pubertal rise in gonadal hormones generates sex differences in approach-avoidance behaviors that may impact psychiatric vulnerability. To examine the influence of pubertal development on adult behavior, we removed the gonads or performed sham surgery in male and female mice just prior to puberty onset and assessed performance in an odor-guided foraging task and anxiety-related behaviors in adulthood. We observed no significant sex differences in foraging or anxiety-related behaviors between intact adult male and female mice but found significant differences between adult male and female mice that had been gonadectomized (GDX) prior to puberty onset. GDX males failed to acquire the odor-guided foraging task, showed reduced locomotion, and exhibited increased anxiety-like behavior, while GDX females showed the opposite pattern of behavior. These data suggest that puberty may minimize rather than drive differences in approach-avoidance phenotypes in male and female mice. 

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2. Neuroendocrinology of Sex-Role Reversal

   https://doi.org/10.1093/icb/icaa046  

   Lipshutz, Sara E; Rosvall, Kimberly A (May 2020, Integrative and Comparative Biology)

   Synopsis Females of some species are considered sex-role reversed, meaning that they face stronger competition for mates compared to males. While much attention has been paid to behavioral and morphological patterns associated with sex-role reversal, less is known about its physiological regulation. Here, we evaluate hypotheses relating to the neuroendocrine basis of sex-role reversal. We refute the most widely tested activational hypothesis for sex differences in androgen secretion; sex-role reversed females do not have higher levels of androgens in circulation than males. However, we find some evidence that the effects of androgens may be sex-specific; circulating androgen levels correlate with some competitive phenotypes in sex-role reversed females. We also review evidence that sex-role reversed females have higher tissue-specific sensitivity to androgens than males, at least in some species and tissues. Organizational effects may explain these relationships, considering that early exposure to sex steroids can shape later sensitivity to hormones, often in sex-specific ways. Moving forward, experimental and correlative studies on the ontogeny and expression of sex-role reversal will further clarify the mechanisms that generate sex-specific behaviors and sex roles. 

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3. Caught in the middle: Variation in the physical and behavioral development of male olive baboons (Papio anubis)

   Hawks, Kale A; Most, Corinna A (March 2024, American journal of biological anthropology)

   Male baboons mature more slowly than females, reaching full adult maturity at around 10-12 years of age. After the onset of puberty at 5-7 years, the sub-adult period lasts 3-5 years while the male continues to grow, though there is considerable variation between individuals. Here, we present data on the behavioral changes that accompany the physical maturation of male olive baboons (Papio anubis) as they transition through each developmental stage. This research was conducted on a fully habituated wild troop at the Uaso Ngiro Baboon Project in Laikipia, Kenya. We use long-term grooming data (2018-2023) to show that males have significantly more grooming partners as they get older (n=48, p<.001). We then use behavioral data collected in June and July 2023 to compare the social behaviors of males from three developmental stages: juveniles (n=5), males who recently became sub-adults (n=4), and males who have been sub-adults for over a year (n=5). The differences between these three groups show the effect of puberty on behavior: juveniles were observed in social play significantly more often than sub-adults (p=.006), while males who recently underwent puberty tended to groom less often than either juveniles or older sub-adults (p=.091). Our focal data also revealed variation in the age at which males reached each developmental stage. Further research is needed to determine causes and consequences of the variation in age at puberty and the potential long-term consequences of this variation on the males’ social behavior. 

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4. Hypocretin in the nucleus accumbens shell modulates social approach in female but not male California mice

   https://doi.org/10.1038/s41386-024-01937-9  

   Luo, Pei_X; Serna_Godoy, Alexandra; Zakharenkov, Hannah_Cortez; Vang, Nou; Wright, Emily_C; Balantac, Taylor_A; Archdeacon, Sinéad_C; Black, Alexis_M; Lake, Alyssa_A; Ramirez, Alison_V; et al (August 2024, Neuropsychopharmacology)

   Abstract The hypocretin (Hcrt) system modulates arousal and anxiety-related behaviors and has been considered as a novel treatment target for stress-related affective disorders. We examined the effects of Hcrt acting in the nucleus accumbens shell (NAcSh) and anterodorsal bed nucleus of the stria terminalis (adBNST) on social behavior in male and female California mice (Peromyscus californicus). In female but not male California mice, infusion of Hcrt1 into NAcSh decreased social approach. Weak effects of Hcrt1 on social vigilance were observed in both females and males. No behavioral effects of Hcrt1 infused into the adBNST were observed. Analyses of sequencing data from California mice andMus musculusNAc showed thatHcrtr2was more abundant thanHcrtr1, so we infused the selective Hcrt receptor 2 antagonist into the NAcSh, which increased social approach in females previously exposed to social defeat. A calcium imaging study in the NAcSh of females before and after stress exposure showed that neural activity increased immediately following the expression of social avoidance but not during freezing behavior. This observation is consistent with previous studies that identified populations of neurons in the NAc that drive avoidance. Intriguingly, calcium transients were not affected by stress. These data suggest that hypocretin acting in the NAcSh plays a key role in modulating stress-induced social avoidance. 

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5. Juvenile social dynamics reflect adult reproductive strategies in bottlenose dolphins

   https://doi.org/10.1093/beheco/araa068  

   Galezo, Allison A; Foroughirad, Vivienne; Krzyszczyk, Ewa; Frère, Céline H; Mann, Janet (July 2020, Behavioral Ecology)

   Taborsky, Michael (Ed.)

   Abstract The juvenile period is a challenging life-history stage, especially in species with a high degree of fission–fusion dynamics, such as bottlenose dolphins, where maternal protection is virtually absent. Here, we examined how juvenile male and female bottlenose dolphins navigate this vulnerable period. Specifically, we examined their grouping patterns, activity budget, network dynamics, and social associations in the absence of adults. We found that juveniles live in highly dynamic groups, with group composition changing every 10 min on average. Groups were generally segregated by sex, and segregation was driven by same-sex preference rather than opposite-sex avoidance. Juveniles formed strong associations with select individuals, especially kin and same-sex partners, and both sexes formed cliques with their preferred partners. Sex-specific strategies in the juvenile period reflected adult reproductive strategies, in which the exploration of potential social partners may be more important for males (which form long-term alliances in adulthood) than females (which preferentially associate with kin in adulthood). Females spent more time alone and were more focused on foraging than males, but still formed close same-sex associations, especially with kin. Males cast a wider social net than females, with strong same-sex associations and many male associates. Males engaged in more affiliative behavior than females. These results are consistent with the social bonds and skills hypothesis and suggest that delayed sexual maturity in species with relational social complexity may allow individuals to assess potential associates and explore a complex social landscape without the risks associated with sexual maturity (e.g., adult reproductive competition; inbreeding). 

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